Summary 



Several standard drag-burial anchors including fluke, pick, and mud 

 types were evaluated to determine the maximum practicable sizes that could 

 be fabricated, handled, and deployed. The maximum size, 45 Mg to 68 Mg 

 (100,000 to 150,000 lbs), will be controlled strictly by fabrication 

 capability. The capability to handle and deploy components of this 

 magnitude is well established. 



Table 7 summarizes the characteristics of the possible anchors for 

 OTEC. Maximum recommended sizes are 68 Mg (150,000 lbs) for a welded 

 fluke type anchor and 45 Mg (100,000 lbs) for a cast anchor. Casting is 

 the only reasonable method for fabricating the Bruce (pick type) anchor 

 since its shape is not amendable to welded construction. A 64 Mg 

 (140,000 lbs) cast anchor is conceded as a possiblity within the present 

 state-of-the-art with the realization that limited data exists in cast- 

 ings of this size. Anchor cost varies from 1 to 3 cents per newton 

 (6 to 12£ per pound) of holding capacity. In practice these differences 

 would not be as significant because the higher cost is associated with a 

 higher capacity anchor; thus, the number of mooring legs would be reduced 

 with commensurate savings in materials and installation costs. Anchor 

 size differences are not significant provided the fluke type, anchor employs 

 hinges in the stabilizer bars; otherwise, the approximately 12.2 m (40 ft) 

 width would complicate deployment. 



The drag burial anchors discussed are feasible to lateral capacities 

 to 22 MN (5x106 lbs). The difficulties inherent in using standard drag 

 anchors in combination makes this type unsuitable for the Gulf Stream sites 

 where loads to 178 MN (40x10^ lbs) are possible. It is ^jery doubtful that 

 eight of these large anchors could be placed in parallel such that each 

 would be equally loaded. 



Even in the deep water, benign environments where the lateral loads 

 range only up to 18 MN (4x10° lbs), drag anchors are not desirable. This 

 is true because the drag embedment anchor requires a zero mooring line 

 angle with the seafloor in order to embed, and requires that a near-zero 

 angle be maintained in order to realize best holding capacity. Also, the 

 drag embedment anchor is able to resist load from only one direction. 

 These requirements of near-zero mooring line angles and uni-directional 

 loading are too restrictive for general OTEC application. 



The above requirements for drag embedment anchors can be satisfied. 

 For instance, the uni-directional loading requirement can be met by using 

 a multi-point moor in which each individual leg and its anchor experience 

 service load is essentially from one direction. The requirement of zero 

 mooring line angle during anchor embedment can be achieved in at least 

 three ways: 



1. A sufficiently long scope of line could be used such that the 

 mooring line angle at the seafloor was zero. However, the cost of the 

 long line will be quite high, and the following techniques for shortening 

 the scope will likely prove more cost effective. 



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